ROPE-MAKING 



ROMAN AXiTTM. An alum extracted from tho volcanic rocks of the Solfatara ; 

 it contains more alumina than the common alum. See ALUM. 



RO1YXAN CEMENTS. Under the name of Roman cement, some hydraulic mor- 

 tars, varying considerably in their chemical composition, though physically possessing 

 tho same general character, are sold. Like all the hydraulic cements, it is an 

 argillaceous lime. It is usually manufactured from a dark brown stone a carbonate 

 of lime with much alumina found in the Island of Sheppy. This stone is calcined 

 and mixed with a certain proportion of sand. 



Any hydraulic limestone, that is, one containing from 15 to 20 per cent, of clay, 

 will, when properly prepared, form this cement. Calcine any ordinary clay, and 

 mix it with two-thirds its quantity of lime, grind to powder and calcine again ; this 

 makes a very beautiful cement, improperly called Roman, since the preparation was 

 entirely unknown to the Romans. See HYDRAULIC CEMENT. 



ROMAN OCHRE. A deep and powerful orange-yellow colour, transparent and 

 durable. It is used both raw and burnt by artists. The colouring-matter is oxide 

 of iron mixed with earthy matter. See OCHRE. 



ROMAN- VITRIOL. See CoPPEH. 



HOOPING, ASPHALTE. Patent asphalte roofing felt, particularly applicable 

 for warm climates. It is a non-conductor. It is portable, being packed in rolls, and 

 not being liable to damage in carriage, it effects a saving of half the timber usually 

 required. It can be easily applied by any unpractised person. From its lightness, 

 weighing only about 42 Ibs. to tho square of 100 feet, the cost of cartage is small. 

 The felt can be laid on from gable to gable, or across the roof from eaves to eaves. 

 It is essential that it should be stretched tight and smooth, overlapping full one inch 

 at the joinings, and closely nailed through the overlap with twopenny fine clout nails 

 (heated in a shovel and thrown when hot into grease to prevent rust), about l inch 

 apart, but copper nails are preferable. 



Tho whole roof must have a good coating of coal-tar and lime (about two gallons 

 of the former to six pounds of the latter), well boiled together, kept constantly 

 stirring while boiling, and put on hot with a common tar mop, and while it is soft, 

 some coarse sharp sand may be sifted over it. The coating must be renewed every 

 fourth or fifth year, or more or less frequently according to tho climate. The gutters 

 should be made of two folds, one over the other, cemented together with the boiling 

 mixture. 



ROOFING-SXiAT&. See SLATE. 



ROPE-MAKING. The fibres of hemp which compose a rope seldom exceed fn 

 length 3^ feet at an average. They must, therefore, be twined together so as to unite 

 them into one; and this union is effected by the mutual circumtorsion of the two 

 fibres. If the compression thereby produced be too great, the strength of the fibres 

 at the points where they join will be diminished ; so that it becomes a matter of great 

 consequence to give them only such a degree of twist as is essential to their union. 



The first part of the process of rope-making by hand, is that of spinning the yarns, 

 or threads, which is done in a manner analogous to that of ordinary spinning. The 

 spinner carries a bundle of dressed hemp round his waist ; the two ends of the bundle 

 being assembled in front. Having drawn out a proper number of fibres with his 

 hand, he twists them with his fingers, and fixing this twisted part to the hook of a 

 whirl, which is driven by a wheel put in motion by an assistant, he walks backwards 

 down the rope-walk, the twisted part always serving to draw out more fibres from the 

 bundle round his waist, as in the flax spinning-wheel. The spinner takes care that 

 these fibres are equally supplied, and that they always enter the twisted parts by their 

 ends, and never by their middle. As soon as he has reached the termination of the 

 walk, a second spinner takes the yarn off the whirl, and gives it to another person to 

 put upon a reel, while he himself attaches his own hemp to the whirl-hook, and pro- 

 ceeds down the walk. When the person at the reel begins to turn, the first spinner, 

 who has completed his yarn, holds it firmly at the end, and advances slowly up the 

 walk, while the reel is turning, keeping it equally tight all the way, till he reaches 

 the reel, where ho waits till the second spinner takes his yarn off the whirl-hook, and 

 joins it to the end of that of the first spinner, in order that it may follow it on the reel. 



The next part of the process is that of warping the yarns, or stretching them all 

 to one length, which is about 200 fathoms in full-length rope-grounds, and also in 

 putting a slight turn or twist into them. 



The third process in rope-making is tho tarring of the yarn. Sometimes tho yarns 

 are made to wind off one reel, and, having passed through a vessel of hot tar, are 

 wound upon another, the superfluous tar being removed by causing the yarn to pass 

 through a hole surrounded with spongy oakum ; but the ordinary method is to tar it in 

 skeins or hanks, which are drawn by a capstan with a uniform motion through the 

 tar-kettle. Yarn for cables requires more tar than for hawser-laid ropes ; and for 



